Black Friday is mostly for the US I suppose. Since a huge chunk of volume comes from China, even if US merchants cashed out into fiat Chinese traders will still cover for them. Overall I think we won't see an effect.
So far there doesn't seem to be much effect on the Bitcoin price. Here in Europe where I live, black friday is quite calm, not much action here as we are more interested in the Christmas time. That's when the people here go nuts on buying stuff.